Demolition hammers are used on work sites to break up objects such as rocks, concrete, asphalt, frozen ground, or other hard objects. The hammers may be mounted to machines, such as backhoes and excavators, or may be hand-held. The hammers may be powered by a hydraulic or pneumatic pressure source. In operation, a high pressure fluid drives a piston to strike a tool bit, which in turn, strikes rock, concrete, asphalt or other hard object to be broken up.
Lubrication systems are used to supply lubricant, such as grease, to bearing surfaces in the hammer to reduce friction between moving parts, such as between the tool bit and bushings that are used to align the tool bit. The lubrication system may be separate from the hammer, for example by being mounted on a carrier machine, or mounted to the hammer, i.e., an on-board system. Whether externally mounted or on-board, a lubricant supply is provided with the system. Operating the hammers without lubrication can result in significant damage to the hammer. In order to monitor the amount of lubricant remaining, many systems provide inspection windows, so that an operator can visually monitor the amount of lubricant remaining. Such systems, however, are dependent on the operator taking the necessary steps to manually check the window.
In the system of U.S. Pat. No. 8,689,940 B2 to Jagdale, et al., a lubrication system having moveable a valve member is configured to divert drive fluid to shutdown or derate the tool. The valve member is actuable in response to engagement by a projection on a plunger disposed within the lubricant reservoir. The plunger follows the lubricant within the lubricant reservoir and when the lubricant reaches a low level, the projection engages and actuates the valve member. When the valve member moves from a first to a second position, it opens a passageway to a drive fluid outlet which diverts drive fluid back to the drive fluid source.